But there are other ways to make vehicles greener, including the use of renewable materials to replace petroleum-derived synthetic components.

For its all-new 2013 Escape crossover, Ford has created door bolsters from a plant called kenaf. The bolsters, which insulate the interior from road noise, were made from oil-based resins in previous Escape models.

Kenaf is a tropical plant in the hibiscus family, related to both cotton and okra. It most closely resembles bamboo.

Its oil is widely used in the cosmetics industry, and its upper leaves and shoots are edible. Fibers from the kenaf plant can be used in paper, cardboard, and other packaging materials as well.

The door bolsters in the 2013 Ford escape--basically stuffing inside the door panel--are made from a 50-50 mixture of kenaf and polypropylene. Ford says this reduces its use of oil-based resin by 300,000 pounds per year.

The kenaf-based door bolsters have another advantage as well: They're 25 percent lighter than those in the superseded Escape.